Over the last decade or so, some electronic systems such as telephone switching facilities or main frame computers and the like have demonstrated a convergence of technologies. Likewise, these apparatuses have taken on a general sameness of physical appearance, particularly in the retainment of circuit board elements. Each of the systems of interest is characterized by an equipment shelf having circuit board slides being arranged in parallel one with another, in a row, for receiving edge surfaces of a plurality of circuit boards. A circuit board is inserted from a front side of the equipment shelf into a pair of the circuit board slides where the circuit board is retained, and it is electrically and/or optically connected into the system by conductors carried by a back plane at a back side of the equipment shelf. One example of this structure is found in U.S. Pat. No. 4,787,081, issued on Nov. 22, 1988 and entitled "TIME DIVISION MULTIPLEX EQUIPMENT SHELVES", which at a glance, may appear to be similar, but have remained distinct because of design variations in circuit board dimensions which of course dictate like differences in slide spacing and depth. Such distinct variations are not limited between systems but may also exist within a system of any one type. One reason for variation is that some circuit boards generate more heat than others, while in operation. It is desirable to arrange circuit boards, in an equipment shelf, with a minimum of space therebetween in order to maximize the use of space in any given system. However the minimum spacing attainable between circuit boards can be dictated by several factors, one of which is providing for adequate ventilation to allow for dissipation of heat generated by normal operation of the circuit boards.
My application for patent, entitled "EQUIPMENT SHELF", was filed in Canada on Sept. 29, 1989, and is identified with Ser. No. 614,700. My application teaches that the expense of inventory associated with the variety and number of piece parts typically required for the manufacture of various equipment shelves used in some electronic systems may be reduced.
In one example, the equipment shelf includes a plurality of circuit board slides, each having an elongated body with a groove in one side thereof, for receiving an edge of a circuit board, and a plurality of attachment projections extending from another side thereof. The circuit board slides are grouped in pairs, each for slidably engaging opposite edges of a circuit board. First and second side panels are spaced apart by a plurality of elongated cross connecting members, which receive the attachment projections in retaining means facing the circuit board locations. One of the advantages of this equipment shelf is that each of the elongated spacing members is provided by an extrusion which is cut to length for assembly. In assembly, each of the elongated spacing members is orientated to fit at its location where it is secured in place by screw threaded fasteners. Each extrusion is shaped to receive retaining means in the form of a thin flat strip with holes formed therein at predefined locations, for fastening the board slides. However, this assembly is at some disadvantage, as each spacing member is a little wider than it would otherwise be, in order to facilitate the feature of adaptability. This greater width has been observed to have an adverse effect upon otherwise satisfactory ventilation characteristics of the equipment shelf. Air flow required for cooling during operation is somewhat restricted by the width of each of the cross connecting members. This width is convenient for providing the adaptability of the equipment shelf and may be compensated for by positioning the circuit boards at greater than typical spacing, to obtain adequate ventilation. However, increased spacing of the circuit boards may also increase the amount of floor space required to accommodate the electronic system.
It is an object of the present invention to improve ventilation of circuit boards retained in an adaptable equipment shelf.